Techniques for detecting, analyzing, and using visible authentication patterns
First Claim
1. A digital representation of an analog signal, the digital representation being characterized in that:
- the digital representation includes a representation of a copy detection signal whose sensitivity to transformations produced by digital-to-analog and analog-to-digital conversions is not based on a watermark contained in the copy detection signal,the representation of the copy detection signal being comparable with the copy detection signal of another digital representation to determine a copying relationship of the analog signal to the other digital representation of the analog signal.
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Abstract
Improved techniques for making copy detection patterns and using them to detect copying relationships between digital representations. The techniques include techniques for including a message in a copy detection pattern without altering the copy detection patterns entropy and reading the message, techniques for using a copy detection pattern on an analog form to determine whether the analog form is an original analog form without reference to a digital representation of the original of the analog form'"'"'s copy detection pattern, techniques for increasing the sensitivity of copy detection using copy detection patterns by modifying one of two copy detection patterns that are being compared to take into account alterations resulting from the copying process, techniques for distributing a copy detection pattern across a document, and techniques for using the entropy of a copy detection pattern to locate the copy detection pattern. Also disclosed are applications of copy detection patterns with copying that involves transformations between the digital and analog forms and with digital-to-digital copying.
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Citations
31 Claims
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1. A digital representation of an analog signal, the digital representation being characterized in that:
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the digital representation includes a representation of a copy detection signal whose sensitivity to transformations produced by digital-to-analog and analog-to-digital conversions is not based on a watermark contained in the copy detection signal, the representation of the copy detection signal being comparable with the copy detection signal of another digital representation to determine a copying relationship of the analog signal to the other digital representation of the analog signal.
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2. A method of creating a digital authentication pattern that permits non-watermark-based determination of a copying relationship of a digital representation of an object with which the digital authentication pattern is associated, the digital authentication pattern containing a message, the digital authentication pattern belonging to a digital representation of an object with which the digital authentication pattern is associated, and the digital authentication pattern including a plurality of pattern elements that have pattern element values and the method comprising:
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selecting a set of the pattern elements to represent message elements of the message; and for a pattern element belonging to the selected set of pattern elements, setting the pattern element'"'"'s pattern element value to represent the message element such that setting the pattern element'"'"'s value to represent the message element leaves the digital authentication pattern'"'"'s usefulness in determining the copying relationship substantially unchanged. - View Dependent Claims (3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A digital authentication pattern that permits non-watermark-based determination of a copying relationship of a digital representation of an object with which the digital authentication pattern is associated, the digital authentication pattern containing a message and the digital authentication pattern comprising:
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a plurality of pattern elements, the plurality of pattern elements including a set of the pattern elements that represent message elements of the message; and in a pattern element that represents a message element, the value of the pattern element is set such that setting the value of the pattern element to represent the message element leaves the digital authentication pattern'"'"'s usefulness in determining the copying relationship substantially unchanged. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20, 21)
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22. A method of reading a message contained in a digital authentication pattern, the digital authentication pattern permitting non-watermark-based determination of a copying relationship of a digital representation of an object with which the digital authentication pattern is associated, the digital authentication pattern including a plurality of pattern elements having pattern element values, the pattern elements including a set of pattern elements that have pattern element values representing message elements of the message, the values of the set of pattern elements having been set to represent the message elements such that the digital authentication pattern'"'"'s usefulness in determining the copying relationship remains substantially unchanged, and the method comprising:
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selecting the set of the pattern elements whose pattern element values represent message elements of the message; and for each pattern element belonging to the selected set, comparing the pattern element with equivalent pattern elements that have a possible message element value to determine the message element values of the message elements in the selected set. - View Dependent Claims (23, 24, 25, 26, 27, 28, 29, 30, 31)
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Specification